This core will provide tissue culture-derived reagents for all four projects. The core will make and titer stocks of mutant and wt forms of v-abl and bcr-abl viruses. The core will also use these viruses to transform murine bone marrow cells and fibroblast ell lines in vitro and to infect mice in vivo. The core will also obtain from different projects wt and mutant forms of Jak and Abi-1 proteins and will generate stably transfected lines expressing these proteins in an inducible manner. The core will generate monoclonal antibodies and will provide routine cell culture and freezing for all of the projects.